But Merritt's family has warned against a knee-jerk reaction to his death.

"Jack would not want this terrible, isolated incident to be used as a pretext by the government for introducing even more draconian sentences on prisoners, or for detaining people in prison for longer than necessary," they said.

Justice minister Robert Buckland told BBC radio he was meeting officials on Monday to review the licence conditions of every convicted terrorist released from prison.

Buckland said it would also look at those "about to be released and also a wider group who weren't convicted of terrorism offences but who present an extremist risk".

Buckland said any prisoner on early release had been stopped from going to events similar to the rehabilitation conference attended by Usman Khan near London Bridge on Friday.